1. Field of the Invention
The present invention relates to a tool to be attached to a spindle of a machine tool for machining a workpiece.
2. Description of the Related Art
In, for example, a machining center or other machine tool provided with a spindle, the maximum rotational speed of the spindle (per unit time) is determined by the structure of a the main bearing rotatably supporting the spindle and a its lubrication system. For this reason, when desiring to rotate a tool at a speed higher than the maximum rotational speed of the spindle, an accelerating apparatus is used.
An example of a known accelerating apparatus holds the tool and is able to be attached to the spindle. The accelerating apparatus increases the rotary force of the spindle by a gear mechanism, such as epicyclic gearing, to increase the rotational speed of the tool.
For example, in a machining center, when it is desired to increase the rotational speed of the tool to higher than the maximum speed of the spindle temporarily, such an accelerating apparatus is attached to the spindle in the same way as an ordinary tool to enable the tool to be rotated at a higher rotational speed.
However, when raising the rotational speed of the tool to a higher speed than the spindle by the above accelerating apparatus comprised of the gear mechanism, the accelerating apparatus increasingly generates heat at a super high rotational speed, e.g., tens of thousands to hundreds of thousands of revolutions per minute, such that the machining tolerance of a workpiece can be influenced by the heat. Furthermore, at the above super high rotational speed, the noise from the accelerating apparatus can also increase. Accordingly, a highly reliable, precise structure, able to withstand the above super high rotational speed, is required for the accelerating apparatus. A disadvantage to such a structure is that the manufacturing cost becomes relatively high.
In an accelerating apparatus with a gear mechanism, it is necessary to lubricate the gear or bearing using a supply passage and a discharge passage for lubricating oil in the accelerating apparatus. A disadvantage to such a lubrication system is that the apparatus becomes larger and it is more difficult to automatically change the tool by an automatic tool changer.
Another accelerating method is using a high frequency motor for driving the tool, and supplying drive current to this high frequency motor from a specially provided control apparatus so as to rotate the tool at a high speed. However, since there is a cable for supplying electric power externally, there are the disadvantages that it is difficult to automatically change tools, and the cost of the facilities is increased.
An object of the present invention is to provide a tool and a tool holder attachable to a spindle of a machine tool by an automatic tool changer in the same manner as an ordinary tool, capable of giving a higher rotational speed than the speed of the spindle of the machine tool without the supply of electric power externally. The tool and tool holder are capable of operating without connection to an external power supply, and they are made compact to be changed automatically.
Another object of the present invention is to provide a machine tool including the above tool and tool holder.
According to a first embodiment of the present invention, there is provided a tool attachable to a spindle of a machine tool including a machining tool for machining a workpiece; a motor for driving the machining tool; and a generator electrically coupled to said motor to which rotary force is transmitted from a spindle of the machine tool and thereby generating electric power to drive the motor and; sealed bearings including a lubricating oil rotatably supporting a transmitting member for transmitting rotary force of the spindle to the generator, and a drive shaft for transmitting rotary force generated by the motor to the machining tool.
The tool can further include an attachment part serving as the transmitting member attachable to the spindle and transmitting rotary force of the spindle to the motor, and a case for rotatably holding the attachment part and a drive shaft of the motor through the bearings and engaging with a non-rotating portion of the machine tool so as to be restricted from rotation.
The generator can be an alternating current generator which supplies voltage of a frequency in accordance with the rotational speed of the spindle to the motor, and the motor can be an induction motor rotating by the rotational speed in accordance with a frequency.
According to a second embodiment of the present invention, there is provided a tool holder able to hold a machining tool for machining a workpiece and attachable to a spindle of a machine tool, including a tool holding part for rotatably holding the machining tool; a motor for rotating the tool holding part; and a generator electrically coupled to the motor, to which rotary force is transmitted from a spindle of the machine tool and generating electric power to drive the motor; and sealed bearings including a lubricating oil rotatably supporting a transmitting member for transmitting rotary force of the spindle to the generator, and a drive shaft for transmitting rotary force generated by the motor to the machining tool.
The tool holder can further include an attachment part serving as the transmitting member attachable to the spindle and transmitting rotary force of the spindle to the motor, and a case for rotatably holding the attachment part and a drive shaft of the motor through the bearings and engaging with a non-rotating portion of the machine tool so as to be restricted from rotation.
The generator can be an alternating current generator which supplies voltage of a frequency in accordance with the rotational speed of the spindle to the motor, and the motor can be an induction motor rotating by the rotational speed in accordance with a frequency.
According to a third embodiment of the present invention, there is provided a machine tool including a machine tool body provided with a spindle, a drive means for driving the spindle, and at least one control axis for changing a relative position between the spindle and a workpiece; a tool, attachable to the spindle, and provided with a machining tool for machining a workpiece, a motor for driving the machining tool, and a generator, electrically coupled to the motor, to which rotary force is transmitted from the spindle and thereby generating electric power for driving the motor; a control apparatus for controlling the drive of the drive means and the control axis in accordance with a machining program; and in the tool, sealed bearings including a lubricating oil rotatably supporting a transmitting member for transmitting rotary force of the spindle to the generator, and a drive shaft for transmitting rotary force generated by the motor to the machining tool.
The machine tool can further include an automatic tool changer for attaching the tool to the spindle.
According to a fourth embodiment of the present invention, there is provided a tool attachable to a spindle of a machine tool including a machining tool for machining a workpiece; a motor for driving the machining tool; a generator, electrically coupled to the motor, for generating electric power to drive the motor; an attachment part for transmitting rotary force to the generator from the spindle and to be attached to the spindle; a casing for holding the motor and the generator, rotatably holding the attachment part, and forming a cooling groove for circulating a coolant for cooling the motor and the generator; and a locking part provided at the casing, engaging with a non-rotating part near the spindle for restricting rotation, and formed with a hole for supplying the coolant from the non-rotating part; the tool supplying coolant from the locking part to the tool and circulating the coolant to the cooling groove so as to cool the tool itself and cool the generator and motor.
The casing can circulate the coolant to the cooling groove, then discharge it from an end of the cooling groove to the outside of the tool.
According to a fifth embodiment of the present invention, there is provided a tool holder able to hold a machining tool for machining a workpiece and attachable to a spindle of a machine tool body, including a tool holding part for rotatably holding the machining tool; a motor for rotating the tool holding part; a generator, electrically coupled to the motor, for generating electric power for driving the motor; a casing for holding the motor and the generator, and forming a cooling groove for circulating a coolant for cooling the motor and the generator; and a locking part provided at the casing, engaging with a non-rotating part near the spindle for restricting rotation, and formed with a hole for supplying the coolant from the non-rotating part; the tool supplying coolant from the locking part to the tool and circulating the coolant to the cooling groove so as to cool the tool holder itself and cool the generator and motor.
According to a sixth embodiment of the present invention, there is provided a machine tool including a machine tool body provided with a spindle, a drive means for driving the spindle, and at least one control axis for changing a relative position between the spindle and a workpiece; a tool to be attached to the spindle; and a control apparatus for controlling the drive of the drive means and the control axis in accordance with a machining program; wherein the tool is provided with a machining tool for machining a workpiece, a motor for driving the machining tool, a generator, electrically coupled to the motor, for generating electric power to drive the motor, and a cooling means for cooling the tool itself and cooling the motor and the generator.
According to a seventh embodiment of the present invention, there is provided a tool to be attached to a spindle of a machine tool, comprising a machining tool for machining a workpiece; a motor for driving the machining tool; a generator, electrically coupled to the motor, for generating electric power to drive the motor; an attachment part having a first channel for carrying a cooling medium for cooling the tool and a second channel formed from the middle of the first channel at an outer diameter side near the generator and connected to the first channel, transmitting rotary force to the generator from the spindle, and to be attached to the spindle; a casing having a third channel for carrying a coolant provided so as to connect a space at the generator side and a space at the motor side and continuing from the second channel, holding the motor and the generator, and rotatably holding the attachment part; and a locking part provided at the casing and engaging with a non-rotating part near the spindle for restricting rotation.
The casing can circulate the coolant to the tool, then discharge it from a front end of the casing to the outside of the tool.
According to an eighth embodiment of the present invention, there is provided a tool holder able to hold a machining tool for machining a workpiece and attachable to a spindle of a machine tool body, including a tool holding part for rotatably holding the machining tool; a motor for rotating the tool holding part; a generator, electrically coupled to the motor, for generating electric power for driving the motor; an attachment part having a first channel for carrying a cooling medium for cooling the tool holder and a second channel formed from the middle of the first channel at an outer diameter side near the generator and connected to the first channel, transmitting rotary force to the generator from the spindle, and to be attached to the spindle; a casing having a third channel for carrying a coolant provided so as to connect a space at the generator side and a space at the motor side and continuing from the second channel, holding the motor and the generator, and rotatably holding the attachment part; and a locking part provided at the casing and engaging with a non-rotating part near the spindle for restricting rotation.
According to a ninth embodiment of the present invention, there is provided a machine tool including a machine tool body provided with a spindle, a drive means for driving the spindle, and at least one control axis for changing a relative position between the spindle and a workpiece; a tool to be attached to the spindle; and a control apparatus for controlling the drive of the drive means and the control axis in accordance with a machining program; wherein the tool is provided with a machining tool for machining a workpiece, a motor for driving the machining tool, a generator, electrically coupled to the motor, for generating electric power to drive the motor, and a cooling means having a channel for carrying a coolant from a rear center of an attachment part from the spindle side, cooling the tool itself, and cooling the motor and the generator.
In the first to third embodiments of the present invention, a tool to be attached to the spindle is provided with a generator electrically coupled to a motor, electric power is generated using the rotary force of the spindle, and the generated electric power is used to drive the motor and rotate the machining tool. Accordingly, it is possible to drive the tool without connection with an external power source, and automatic tool changing is facilitated.
Thus, the tool of the disclosed embodiments is completely independent from the spindle and any external device. If the bearings used for the disclosed tool are lubricated by supplying lubricant from the spindle or otherwise externally, a supply passage and a discharge passage for the lubricant become necessary, sacrificing the complete independence of the tool from the spindle and external devices, requiring a tool larger in size.
Therefore, in the disclosed embodiments, by using sealed bearings not requiring replenishment of lubricant at the rotating part of the tool, the tool can be completely independent from external apparatuses and can be made more compactly.
In the fourth to sixth embodiments of the present invention, a tool to be attached to the spindle is provided with a generator, electrically coupled to a motor, electric power is generated using the rotary force of the spindle, and the generated electric power is used to drive the motor and rotate the machining tool. Accordingly, it is possible to drive the tool without connection with an external power source, and automatic tool changing is facilitated.
Furthermore, the tool of the disclosed embodiments carries a coolant in the cooling groove provided in the tool for cooling the tool itself and the generator and motor, suppressing heat expansion and deterioration of machining tolerances.
In the seventh to ninth embodiments of the present invention, a tool to be attached to the spindle is provided with a generator, electrically coupled to a motor, electric power is generated using the rotary force of the spindle, and the generated electric power is used to drive the motor and rotate the machining tool. Accordingly, it is possible to drive the tool without connection with an external power source, and automatic tool changing is facilitated.
Furthermore, the tool of the disclosed embodiments carries a coolant from the center of the tool for cooling the tool itself and the generator and motor, suppressing heat expansion and deterioration of machining tolerances.